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authorMatt Redfearn <matt.redfearn@mips.com>2018-04-20 11:23:06 +0100
committerJames Hogan <jhogan@kernel.org>2018-05-15 15:53:44 +0100
commit84002c88599d6b537e54b003f763215be2075243 (patch)
treec413ffe5ba6951644deda48b824e151d9b46d68e /arch/mips/pnx833x
parent840a8b55effdc9a98b115f84b8bbb6a2f5d05226 (diff)
downloadop-kernel-dev-84002c88599d6b537e54b003f763215be2075243.zip
op-kernel-dev-84002c88599d6b537e54b003f763215be2075243.tar.gz
MIPS: perf: Fix perf with MT counting other threads
When perf is used in non-system mode, i.e. without specifying CPUs to count on, check_and_calc_range falls into the case when it sets M_TC_EN_ALL in the counter config_base. This has the impact of always counting for all of the threads in a core, even when the user has not requested it. For example this can be seen with a test program which executes 30002 instructions and 10000 branches running on one VPE and a busy load on the other VPE in the core. Without this commit, the expected count is not returned: taskset 4 dd if=/dev/zero of=/dev/null count=100000 & taskset 8 perf stat -e instructions:u,branches:u ./test_prog Performance counter stats for './test_prog': 103235 instructions:u 17015 branches:u In order to fix this, remove check_and_calc_range entirely and perform all of the logic in mipsxx_pmu_enable_event. Since mipsxx_pmu_enable_event now requires the range of the event, ensure that it is set by mipspmu_perf_event_encode in the same circumstances as before (i.e. #ifdef CONFIG_MIPS_MT_SMP && num_possible_cpus() > 1). The logic of mipsxx_pmu_enable_event now becomes: If the CPU is a BMIPS5000, then use the special vpe_id() implementation to select which VPE to count. If the counter has a range greater than a single VPE, i.e. it is a core-wide counter, then ensure that the counter is set up to count events from all TCs (though, since this is true by definition, is this necessary? Just enabling a core-wide counter in the per-VPE case appears experimentally to return the same counts. This is left in for now as the logic was present before). If the event is set up to count a particular CPU (i.e. system mode), then the VPE ID of that CPU is used for the counter. Otherwise, the event should be counted on the CPU scheduling this thread (this was the critical bit missing from the previous implementation) so the VPE ID of this CPU is used for the counter. With this commit, the same test as before returns the counts expected: taskset 4 dd if=/dev/zero of=/dev/null count=100000 & taskset 8 perf stat -e instructions:u,branches:u ./test_prog Performance counter stats for './test_prog': 30002 instructions:u 10000 branches:u Signed-off-by: Matt Redfearn <matt.redfearn@mips.com> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: Florian Fainelli <f.fainelli@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Namhyung Kim <namhyung@kernel.org> Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/19138/ Signed-off-by: James Hogan <jhogan@kernel.org>
Diffstat (limited to 'arch/mips/pnx833x')
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